1. Field of the Invention
The present invention relates to a contactor control apparatus for controlling contactors connected to a battery assembly. In particular, the present invention relates to a contactor control apparatus controlling contactors according to a counter value.
2. Description of the Related Art
In recent years, a power-supply apparatus using a secondary battery such as a nickel-metal hydride battery having a high energy density (hereinafter, referred to as “a nickel-hydrogen battery”) is used as a power source of a motor and a drive source for various types of loads in an electric vehicle such as a pure electric vehicle (hereinafter, referred to as “PEV”), a hybrid electric vehicle (hereinafter, referred to as “HEV”) or the like. The power-supply apparatus for use in the electric vehicle requires a total voltage of approximately 100V to 350V. Since an output voltage of a single battery (a cell) as a minimum unit constituting the power-supply apparatus is approximately 1.2V, a plurality of single batteries (for example, 100 single batteries) is conventionally connected in series so as to obtain a desired total voltage.
A contactor (relay) for connecting and disconnecting the power supply is provided between the power-supply apparatus and the motor. For example in the PEV, when a driver operates an ignition key to turn on an ignition and turn on the power supply, the contactor is conducted to connect the power-supply apparatus, and as a result, the motor is driven to rotate. When the ignition is turned off, the contactor disconnects the power-supply apparatus and the motor from each other, and as a result, the motor is stopped.
The contactor includes a moving contact and a fixed contact, and further includes a contactor coil for operating the moving contact. In general, the contactor used in the PEV and HEV applies a voltage of an auxiliary power supply that outputs a relatively low voltage, which is generally called an auxiliary battery, to the contactor coil to switch over conductive state and non-conductive state.
However, the auxiliary battery, which is detachably provided in the electric vehicle, may be removed for maintenance or the like or exchanged. If an inappropriate auxiliary battery is mounted or in any similar case, the contactor coil may excessively generate heat and be damaged when a voltage of the auxiliary power supply exceeding a rated voltage of the contactor coils is applied to the contactor coil for a long time interval. The excessive heat generation and the damage of the contactor coil cause malfunctions of the entire electric vehicle.
The Japanese patent laid-open publication No. 10-224901 discloses a contactor control apparatus of a prior art. Referring to FIGS. 11 and 12, the contactor control apparatus of the prior art is described. FIG. 11 shows a configuration of an electric vehicle according to the prior art. In FIG. 11, the electric vehicle includes a battery assembly 1 constituted by a plurality of secondary batteries, a first contactor 2 whose one end is connected to a high-voltage side of the battery assembly 1, a second contactor 3 whose one end is connected to a low-voltage side of the battery assembly 1, a current detector 4 provided in a line on the low-voltage side of the battery assembly 1, a controller 115 connected to the battery assembly 1, the first contactor 2, the second contactor 3 and the current detector 4, a smoothing capacitor 6 connecting another end of the first contactor 2 and another end of the second contactor 3, an inverter 7 connected to both ends of the capacitor 6, and a motor 8 connected to the inverter 7.
The contactors 2 and 3 respectively include a moving contact and a fixed contact, and further include a contactor coil for operation the moving contact. One ends of the respective contactor coils are grounded, while another ends thereof are connected to the controller 115. The respective contactor coils are supplied with the auxiliary power-supply voltage of the auxiliary battery not shown from an auxiliary power-supply voltage input terminal (hereinafter, referred to as “a Vsub terminal”) via the controller 115 to move the moving contacts and switch over between conductive state and non-conductive state of the contacts.
The inverter 7 includes, for example, a plurality of transistors and diodes. The inverter 7 converts a DC power-supply into an AC power-supply and sequentially applies the power-supply voltage supplied from the battery assembly 1 to each phase of the motor 8 so that the motor 8 is rotated.
The smoothing capacitor 6 is provided to reduce a change of the voltage applied to the inverter 7 and stably supply a voltage.
The current detector 4 detects a current flowing in the conductive line on the low-voltage side of the battery assembly 1 and outputs results of the detection to the controller 115.
The controller 115 inputs the current value detected by the current detector 4 and the voltage value of the battery assembly 1. The controller 115 further inputs an operation signal for operating the vehicle from an accelerator, a brake, a shift lever and the like not shown, and controls the contactors 2 and 3 in accordance with the operation signal. The contactors 2 and 3 are controlled in such a manner that the auxiliary power-supply voltage of the auxiliary battery not shown that is inputted from the Vsub terminal is applied to each contactor coil of the contactors 2 and 3 so that the contactors are switched over between conductive state and non-conductive state of the contacts.
The controller 115 compulsorily stops the application of the voltage to the contactor coil when the auxiliary power-supply voltage applied to the contactors 2 and 3 is higher than an uninterruptedly applicable voltage defined by the ratings of the contactor coil to set the contactors in non-conductive state.
Referring to FIG. 12, an operation of the controller 115 is described. FIG. 12 is a timing chart illustrating a change (a) of the voltage applied to the coil and a change (b) of the operation of the second contactor 3. In the example shown in FIG. 12, the uninterruptedly applicable voltage of the contactor coil is set to 16V.
As shown in FIG. 12(a), the voltage applied to the coil exceeds 16V, which is the uninterruptedly applicable voltage of the contactor coils, during a time interval from a timing T2 to a timing T3, a time interval from a timing T4 to a timing T5 and a time interval after a timing T6. Therefore, as shown in FIG. 12(b), the controller 115 switches the contactor to be in non-conductive state (OPEN) during the time interval from the timing T2 to the timing T3, the time interval from the timing T4 to the timing T5 and the time interval after the timing T6.
As described above, the contactor control apparatus according to the prior art is capable of preventing the damage of the contactor by reducing the excessive heat generation in the contactor coil.
However, in the contactor control apparatus according to the prior art, the contactors cannot be conducted when an auxiliary battery whose rated voltage is any higher than the uninterruptedly applicable voltage of the contactor coils is connected as a replacement for emergency or for maintenance, which disadvantageously stops the operation of the electric vehicle.
Further, even when an auxiliary battery having a suitable rated voltage is connected, the electric vehicle is unfavorably often stopped when the voltage value is often increased due to the change of the output voltage of the auxiliary battery.